问题
Can anyone explain me, what is the use of Get Metadata Activity that is newly introduced in ADF V2?
Actually, the information that is given in docs.microsoft.com isn't enough to understand the uses of this Activity.
回答1:
Main purpose of the Get Metadata Activity is:
- Validate the metadata information of any data
- Trigger a pipeline when data is ready/ available
The following example shows how to incrementally load changed files from a folder using the Get Metadata Activity getting filenames and modified Timestamp:
{
"name": "IncrementalloadfromSingleFolder",
"properties": {
"activities": [
{
"name": "GetFileList",
"type": "GetMetadata",
"policy": {
"timeout": "7.00:00:00",
"retry": 0,
"retryIntervalInSeconds": 30,
"secureOutput": false
},
"typeProperties": {
"dataset": {
"referenceName": "SrcLocalDir",
"type": "DatasetReference"
},
"fieldList": [
"childItems"
]
}
},
{
"name": "ForEachFile",
"type": "ForEach",
"dependsOn": [
{
"activity": "GetFileList",
"dependencyConditions": [
"Succeeded"
]
}
],
"typeProperties": {
"items": {
"value": "@activity('GetFileList').output.childItems",
"type": "Expression"
},
"activities": [
{
"name": "GetLastModifyfromFile",
"type": "GetMetadata",
"policy": {
"timeout": "7.00:00:00",
"retry": 0,
"retryIntervalInSeconds": 30,
"secureOutput": false
},
"typeProperties": {
"dataset": {
"referenceName": "SrcLocalFile",
"type": "DatasetReference"
},
"fieldList": [
"lastModified"
]
}
},
{
"name": "IfNewFile",
"type": "IfCondition",
"dependsOn": [
{
"activity": "GetLastModifyfromFile",
"dependencyConditions": [
"Succeeded"
]
}
],
"typeProperties": {
"expression": {
"value": "@and(less(activity('GetLastModifyfromFile').output.lastModified, pipeline().parameters.current_time), greaterOrEquals(activity('GetLastModifyfromFile').output.lastModified, pipeline().parameters.last_time))",
"type": "Expression"
},
"ifTrueActivities": [
{
"name": "CopyNewFiles",
"type": "Copy",
"policy": {
"timeout": "7.00:00:00",
"retry": 0,
"retryIntervalInSeconds": 30,
"secureOutput": false
},
"typeProperties": {
"source": {
"type": "FileSystemSource",
"recursive": false
},
"sink": {
"type": "BlobSink"
},
"enableStaging": false,
"dataIntegrationUnits": 0
},
"inputs": [
{
"referenceName": "SrcLocalFile",
"type": "DatasetReference"
}
],
"outputs": [
{
"referenceName": "TgtBooksBlob",
"type": "DatasetReference"
}
]
}
]
}
}
]
}
}
],
"parameters": {
"current_time": {
"type": "String",
"defaultValue": "2018-04-01T00:00:00Z"
},
"last_time": {
"type": "String",
"defaultValue": "2018-03-01T00:00:00Z"
}
},
"folder": {
"name": "IncrementalLoadSingleFolder"
}
},
"type": "Microsoft.DataFactory/factories/pipelines"
}
See also recently updated documentation.
来源：https://stackoverflow.com/questions/49923091/get-metadata-activity-adf-v2